In the case of a known wire supply device of this kind (DE 89 12 810 U1) the axial slidability of the pay-off spool containing a wire supply is based on the finding that oscillations may be induced at the guide roll which immediately follows the pay-off spool, and these oscillations may be transmitted to the machining span where they may affect the accuracy to size and the surface quality of the workpieces being processed. When the pay-off spool is supported so as not to be movable axially, such oscillations are caused by the fact that the electrode wire, arranged in layers on the spool, is payed off at a different angle at the beginning of each layer than at the end of the layer. From a certain angle on, the electrode wire tends to move up periodically on flanks of a groove formed in the guide roll which receives the wire next down the line from the pay-off spool and then to slide down again into the bottom of the groove. With the known device of the generic kind in question this is prevented by controlled shifting of the pay-off spool so that the electrode wire constantly maintains a certain position at which it runs perpendicularly to the axis of the pay-off spool.
It is also known (JP 07 001 247 A) to wind up spent electrode wire on a take-up spool for disposal, causing the spool to carry out controlled axial reciprocating movements during the winding process in order to make full use of the winding space available.